The elements controlling expression of antibody genes will be analyzed. These include the DNA sequence at the region of transcription of RNA of expressed kappa chains and of the unrearranged kappa locus. In addition kappa genes that are not transcribed will be analyzed. A comparison of these different types will elucidate the requirements for transcription. Further amino acid sequence analysis of related variable (V) regions such as the V 21 group will be carried out to add to our examples of apparent somatic variation of V region genes. Variant sequences will be compared to germline sequences to determine the exact nature of the variation. Such comparisons should lead to an understanding of the mechanism(s) of diversification. Related V region genes will be compared between inbred strains. The basis of the polymorphism at these groups of genes will be analyzed by comparisons of V region genes and their flanking sequences. Serological and chemical methods for identifying VH groups have been developed. These will be applied to an anaysis of serum and surface antibodies in order to assess the number of VH groups (and in turn VH genes) expressed by inbred mice.